Dose-escalating vinblastine for the treatment of canine mast cell tumour

The purpose of this study was to evaluate the short-term adverse events (AEs) in dogs with mast cell tumours (MCT) receiving prednisone and dose-escalating vinblastine (VBL). Twenty-four dogs were treated with intravenous VBL starting at 2 mg m⁻² and then escalating in weekly increments to 2.33, 2.67 and 3 mg m⁻². AEs were graded using a standardized scoring system. No dogs receiving 2 or 2.33 mg m⁻² experienced grade 3 or 4 AEs. Among the dogs, 9.5 and 5.9% had grade 3 or 4 AEs at dosages of 2.67 and 3 mg m⁻², respectively. Serious AEs included neutropaenia (n = 3) and vomiting (n = 1), only one of which required hospitalization. These data indicate that VBL chemotherapy may be safe to administer at higher than the traditional 2 mg m⁻² dosage for dogs with MCT. Randomized prospective trials are necessary to establish whether dose escalation will translate into improved response rates when compared with the standard 2 mg m⁻² dosage.